1. Field of the Invention
This invention relates to fluid flow control valves and more particularly to a valve biased closed when pressure differential across a piston in the valve reaches a critical value.
On installations where fluid moving through a line must be filtered to remove extraneous matter from the liquid it is important that the filter be changed or cleaned prior to being saturated with flow restricting impurities.
In the event the filter is not changed before becoming overloaded with impurities, the filter may rupture and release such impurities downstream which may be detrimental to the equipment or process supplied with the fluid.
This invention provides a valve connected inline with a downstream flow restricting unit. A piston on a valve stem moves a valve to a closed position when pressure differential across the piston exceeds a predetermined value.
2. Description of the Prior Art
I do not know of any patents which are particularly pertinent to this invention. However, one embodiment of this invention employs manually adjustable superposed mating and mismating discs in a downstream flow restricting unit disclosed in my U.S. Pat. Nos. 4,922,950 and 5,080,128 respectively issued to me on May 8, 1990 and Jan. 14, 1992 for Restrictor Valves.